1. Field of the Invention
This invention relates to dual rate spring devices for use in a railroad car truck operated under distinct loading conditions and particularly adapted for use in a railroad car truck where a body of the car is either in a fully loaded or empty condition.
2. Description of the Prior Art
The use of a longer light duty spring disposed within a shorter heavy duty spring to resiliently support a load carrying bolster of a railroad car truck is well known. The longer light duty spring has a sufficient load rate to support the bolster when the car body above is empty or lightly loaded.
When the car body is fully loaded, the light duty spring compresses a sufficient length that the bolster contacts the shorter heavy duty spring such that both springs support the bolster and car body above.
A major problem with presently known dual spring arrangements is that under those conditions in which the heavy duty spring remains unloaded, it is relatively unrestrained to cause excessive noise and produce wear of adjacent parts.
One solution to this problem is disclosed in co-pending application Ser. No. 858,622 wherein a lower end of the outer heavy duty spring is affixed to a retaining cup.